1. Field of the Invention
The invention relates to a pressure reducing valve.
2. Description of Related Art
Generally, a pressure reducing valve (regulator) includes an on-off valve (poppet) between a primary port into which high-pressure gas flows and a secondary port that supplies gas to the outside. As the on-off valve opens and closes, high-pressure gas flowing from the primary port to the secondary port is reduced in pressure, and is then supplied to the outside.
As such a pressure reducing valve, there is a pressure reducing valve that is used in a fuel cell system. An on-off valve (poppet), which is the pressure reducing valve that is used in the fuel cell system, has a variable throttle portion. High-pressure hydrogen gas flowing from the primary port is rapidly reduced in pressure by causing the hydrogen gas to pass through a flow passage that is narrowed by the variable throttle portion, and then the hydrogen gas is conveyed to the secondary port.
That is, the flow passage through which hydrogen gas flows has such a shape that the flow passage cross-sectional area rapidly narrows at a portion just before the variable throttle portion, and has such a shape that the flow passage cross-sectional area rapidly increases at a portion downstream of a portion at which the flow passage of the variable throttle portion is narrowest.
At these portions that are connected to the variable throttle portion and at which the flow passage cross-sectional area changes, such a change that hydrogen gas rapidly compresses and rapidly expands occurs. For this reason, conventionally, turbulence that causes generation of abnormal noise occurs at the portion at which hydrogen gas expands.
In Japanese Patent Application Publication No. 2013-196053 (JP 2013-196053 A), for the purpose of suppressing generation of the above-described unusual noise due to turbulence, turbulence (vortex flow) that occurs in fluid that has passed between a valve seat and a poppet valve is rectified by a fluid rectifying portion provided at a downstream end of the valve seat.
However, in JP 2013-196053 A, it is required to separately or integrally provide the downstream end of the valve seat with a component that forms the fluid rectifying portion. Therefore, there is such an inconvenience that the number of components increases, the number of assembling man-hours increases or the number of processes for forming the fluid rectifying portion increases. In JP 2013-196053 A, turbulence is rectified by the fluid rectifying portion after the turbulence has occurred, so turbulence itself is not suppressed.